Communications networks continue to grow in breadth of coverage and data density. An important enabling technology of this continued growth is increased integration of optical (photonic) components. For example, metropolitan area networks and wide area networks are now being deployed with wavelength division multiplexing (WDM) which add/drop channels using wavelength selective filters integrated onto silicon, or other semiconductor, substrates using very large scale integration (VLSI) manufacturing techniques.
In optical communication there are many applications in addition to wave-length selective filters which to at least some extent utilize a Bragg grating, such as lasers (e.g., distributed Bragg reflector (DBR) laser or distributed feedback (DFB) lasers), grating-assisted couplers, and dispersion compensators to name only a few. One type of integrated Bragg grating, typically referred to a “corrugated grating” is formed by physically corrugating a surface of a waveguide (e.g., planar or rib/ridge waveguides) patterned into a thin film over a substrate. For a first-order corrugated grating to be operative at the 1550 nm wavelength, the grating period, or “tooth” pitch is between about 200 nm and 250 nm. This relatively small feature pitch leaves little latitude for tuning the grating strength (κ) using VLSI manufacturing techniques.